Recent two seater vehicles with a traditional trunk space often incorporate pivoted dual seat backs that can be pulled down one at a time, or together, to open the trunk space up to the rear passenger space. Typically, the lower ends of the legs of the seat back frame contain a closed end slot within which is locked a pivot pin fixed to the vehicle floor, although those two parts can be reversed. It is preferable if the mechanism that locks the pin into the slot, typically called a forkbolt, is passively acting, that is, that the act of pushing the slot over the pin alone acts to engage the lock or latch. A typical example may be seen in U.S. Pat. No. 5,685,612, although the slot and pin there are reversed. The hook is constantly spring loaded to a locked position across the slot, but the pin can kick the hook out of the way as it is pushed into the slot. The hook then springs back passively to the latched position to capture the pin in the sloth. The inherent draw back which any such system is that it does not securely lock the pin into the slot.